Potentiometer constructions



Aug. 29, 1961 M M. MOORE ET A1. 2,998,586

POTENTIOMETER CONSTRUCTIONS Filed June 2e, 1959 L. 22 f5 EB aac United States Patent I 2,998,586 POTENTIOMETER CONSTRUCTIONS Maxwell M. Moore, Arcadia, and Joseph D. Douglas, Pasadena, Calif., assignors to General Controls Co., Glendale, Calif., a corporation of California Filed June 26, 1959, Ser. No. 823,154 2 Claims. (Cl. SSS-145) The present invention relates to potentiometer constructions.

An object of the present invention is to provide an improved potentiometer in which a helically-formed resistance element is used as a driving element for the tap or slider thereon.

Another object of the present invention is to provide an improved potentiometer which is simple and inexpensive to manufacture.

Another object of the present invention is to provide an improved potentiometer of this type having a relatively large resistance range and voltage resolution, yet being of small physical size.

Another object of the present invention is to provide an improved potentiometer in which the resistance element itself is moved in effecting an adjustment of the tap or slider thereon.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIGURE l is a view in side elevation of a potentiometer embodying features of the present invention.

FIGURE 2 is a transverse sectional view taken substantially on line 2--2 of FIGURE 3.

FIGURE 3 is a sectional view taken on line 3-3 of FIGURE l.

FIGURE 4 is a sectional view taken on line 4-4 of FIGURE 5.

FIGURE 5 is a sectional view taken on -line 5-5 of FIGURE 4.

FIGURE 6 is a perspective view of various elements in disassembled form.

FIGURE 7 is a perspective view of a portion of the housing.

FIGURE 8 is a perspective view of the slider.

FIGURES 9, l0 and 1l are perspective views of different 'components shown in the previous figures.

The potentiometer is incorporated in a case or housing comprising an insulated base member 10 and an insulated cover 11 therefor, the base 10 having apertured portions 10A, 10B for convenient mounting.

The resistance element 12 comprises many fine turns of wire 13 wound on a spiral insulated wire 14 with a thin layer of insulation baked on such Wire 14 to insulate the wire 13 from wire 14. Also, the adjacent turns of wire 13 are so spaced to be as close as practical Without adjacent turns touching, i.e. short-circuiting.

In the fabrication of such element 12, the wire 13 may first be coiled on a straight length of insulated wire which is then formed in a spiral as shown. In forming such spiral, the assembly 13, `14 may be spirally wound around insulated shaft 16 which mounts the resistance element 13 between the two end portions 16A and 16B having mounted thereon the slip rings 18 and 19 which are connected respectively to opposite ends of the resistance wire 13 as indicated at 20 and 21.

The end portion 16B is sutiiciently prolonged to fit in the semi-cylindrical bearing 10C in the base 10 `and in the mating semi-cylindrical bearing 11C in cover 11.

`'2,998,586 Patented Aug. 29, 1961 ICC The other end of shaft 16 is journalled for rotation using the following construction.

The adjustment pin or stub shaft 20 is rotatably mounted in complementary semi-cylindrical bearings in the base 10 and cover 11 with the flange 20A on shaft 20 cooperating with complementary grooved portions in such base 10 and cover 11 to prevent axial movement of shaft 2t? when the same is rotated by, for example, a screwdriver engaging the screwdriver adjustment slot 20B. The flange 20A when cooperating with the said complementary grooved portions also forms a labyrinth which facilitates a sealing effect against environmental contaminatlon. The flange 20C on shaft 20 is provided for the same purpose.

This shaft 20 has its end 20D of reduced diameter fitted into the apertured or bored end portion 16D to provide a friction or slip connection therebetween.

A slider 22 in the form of a half nut (FIGURE 8) has a screw-threaded portion 22A with the same matching thread convolutions as the thread defined by resistance element 12. This slider 22, also in the form of a block, is slidably mounted in the base 10 in the rectangular channel 19D defined by the side walls `10E and iilF and the fioor 10G, being guided thereby for movement between the two stops or abutments 10H, 10J.

The slider 22 of insulating material carries the electrical yconducting tap 25 (FIGURES 4 and 1l) which makes electrical contact with the resistance wire 13 on only a portion of one convolution of the spiral 12. This tap 25 is generally double L-shaped as seen in FIGURE ll with the bowed portion 25A adapted to engage the wire 13, with the portion 25B recessed in the slide slot 22B (FIGURE 4), with the portion 25C confined in the slide slot 22C and with the end 25D engaging the contact strip 28 (FIGURES 4 and l0) resting in base 10.

The Contact 25 of resilient nature thus has one of its ends 25A resiliently pressed against the ristance wire 13 and the other one of its ends resiliently pressed against the contact strip 28.

This contact strip 28 extends the full length of the channel in base 10 and is connected electrically to a suitable binding post on the casing base 10 or, as illustrated, may be connected to a fiexible insulated lead 30 which extends through base aperture 10M.

External connections to the two slip rings 18 and 19 may be accomplished in similar manner. As illustrated, slip ring 18 is contacted by the upstanding resilient end 32A of wire 32 which is bent to snugly fit and be self-retained in the base channel 10D. Such wire 32 may be connected to a stationary binding post suitably mounted on base Ill or suitable external connection may be made to wire 32 by a flexible insulated lead 34 extending through channel 10M (FIGURE 2).

Suitable connection may be made to the other slip ring 19 by a resilient wire 36 (FIGURE 2) having one of its ends fitted into a bore in base 10 with an intermediate portion of such wire 36 being either connected to a binding post or to a iiexible insulated wire 38, also extending through the base bore 10M for external connection.

Thus, it will be appreciated that the potentiometer described has many uses. For example, a xed voltage may be applied to the ends of the resistance element 13 through slip rings 18 and 19 and corresponding contacts 32, 36 which are connected to external leads 34 (FiGURE 9) and 38 (FIGURE 6). A voltage is thus developed on the movable tap 25 and this voltage may be adjusted by adjustment of the stub shaft 20.

Upon rotation of shaft 20, the shaft 16 and the resistance element 12 thereon is also rotated, causing the slide block 22 carrying contact 25 to move axially whereupon different portions of resistance element 12 are contacted by contact 25. Such movement of slide block 22 may continue until the slide block engages either abutment or stop 10H or 10J at either one of the limits of travel of block 22 whereupon continued rotation of the stub shaft 20 results in slippage between it and the main shaft 16, i.e. the driving connection 20D, 16D is automatically rendered ineffective at the two limits of movement.

It will thus be seen that the spira-lly wound resistance element 12 serves not only as such but also has a lead screw for producing sliding movement of its tap. This construction allows adjustment with little mechanical eiort.

It will also be seen that the entire -unit may be sealed using conventional sealing means between the base 10 and its lid 11 and between the base 10, shaft 20 and lid 11. Also, a potting compound may be used to seal openings through which the three flexible leads extend.

While the particular embodiments of the present in- 20 vention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader yaspects and, therefore, the aim in the appended claims is to cover all such changes and modifica- '4 tions as fall within the true spirit and 'scope of'this invention.

We claim:

1. A potentiometer comprising a spirally wound resistance element, means producing rotation of the same while limiting axial movement of the same, yand ya slider engaged and moved by said element into engagement with different portions of said element, said slider comprising a generally rectangular block' in the form of ahalf nut engaging a plurality of convolutions of Vsaid element, a base, said element being rotatably mounted on said base, and said slider being slidably mounted in -a groove in said base.

2. A potentiometer as set forth in claim 1 in which a resilient contact element is self-retained on said slider between said slider and said base.

References Cited in the lile of this patent UNITED STATES PATENTS 591,160 Dow Oct. 5, 1897 2,399,060 Puerrner Apr. 23, 1946 2,558,326 Van Dyke June 26, 19,51 2,856,493 Blanco Oct. 14, 1958 2,860,217 Bourns -..7- Nov. 11, 1958 2,886,681 Bourns et al May 12, 1959 

